The reverse is, of course a die-match, but the obverse isn't, which gives us hope of identifying the year of issue!
We already have
Constantius II, who was only made
caesar in 11-324, appearing in the P*AR issue, so this follow-on "dot" issue has to post-date that.
It seems that at
Constantine's mints (or at least at some of them) the
VOT X type continued to 325 AD, then was either dropped or gave way to the
caesar's
VOT XX (
Ticinum) in their decennial year 326 (317+9). Likewise
Constantine's
VOT XX seems to have continued to 324 AD, and then was either dropped or replaced by
VOT XXX in
his vicennalial year 325 (306 + 19).
Ben